Autonomous vehicle driving assist system, method, and program

ABSTRACT

An autonomous vehicle driving assist system, method, and program set a planned route of a vehicle, the planned route including an autonomous driving section where autonomous driving control of the vehicle is permitted, and set a transition exclusion section of the planned route where a transition from autonomous driving control to manual driving is determined to be difficult. The system, method, and program set a transition section of the planned route where the transition from autonomous driving control to manual driving is made, and which excludes the transition exclusion section. Based on the transition section, the system, method, and program determine a section where autonomous driving control is performed in the planned route.

TECHNICAL FIELD

Related technical fields include autonomous vehicle driving assistsystems, methods, and programs which assist a vehicle in traveling byautonomous driving control.

BACKGROUND ART

In recent years, many vehicles are equipped with navigation systems thatprovide the driver with travel guidance of the vehicle, so that thedriver can easily arrive at a desired destination. The navigationsystems are systems that can detect the current location of the vehicleby a GPS receiver etc. and obtain map data corresponding to the detectedcurrent location via a recording medium such as a DVD-ROM or an HDD orvia a network to display the map data on a liquid crystal displaymonitor. The navigation systems also have a route search function tosearch for, when a desired destination is entered, a recommended routefrom the location of the vehicle to the destination. When the obtainedrecommended route is set as a guide route, the navigation systemsdisplay the guide route on a display screen and provide the user withvoice guidance when the vehicle approaches an intersection etc., therebyreliably guiding the user to the desired destination. Recently, somemobile phones, smartphones, tablet computers, personal computers, etc.also have a function similar to that of the navigation systems.

In recent years, in addition to a manual drive mode in which the vehicletravels based on user's driving maneuvers, a drive mode using autonomousdriving control has been proposed as a new drive mode, in which thevehicle autonomously travels along a preset route without user's drivingmaneuvers. For example, in autonomous driving control, the currentlocation of the vehicle, the lane in which the vehicle is traveling, andthe position of other vehicles around are detected as needed, andvehicle control such as control of steering, a driving source, and abrake is autonomously performed such that the vehicle travels along apresent route. The drive mode using autonomous driving control isadvantageous in that it can reduce the burden of driving on the user.However, it is practically difficult for the vehicle to travel only byautonomous driving control in the entire way from the start to the end,and there are also sections where user's manual driving is required. Itis therefore desired to appropriately make a transition from the drivemode using autonomous driving control to the manual drive mode.

For example, Japanese Patent Application Publication No. 2008-290680 (JP2008-290680 A) (pages 4 to 5, FIG. 2) proposes a technique of setting atransition point, or a point where a transition from the drive modeusing autonomous driving control to the manual drive mode is made. Inthis technique, an evacuation area such as a parking area is set betweenthe transition point and an end point of a section where autonomousdriving control can be performed (e.g., an interchange (IC) exit), andthe vehicle is guided to the evacuation area if a transition from thedrive mode using autonomous driving control to the manual drive mode wasnot able to be made at the transition point.

SUMMARY

In the technique described in JP 2008-290680 A, any desired pointlocated before an end point of a section where autonomous drivingcontrol can be performed (e.g., an IC exit) is set as a transitionpoint. However, since the transition point is the point where the userwho was not maneuvering the vehicle starts maneuvering the vehicle, thetransition point need be set in a location that does not impose a greatburden on the user who starts driving the vehicle. For example, if thetransition point is set in a low visibility section or a section wherecomplicated maneuvers are required, the user needs to make suchmaneuvers immediately after the transition although he/she has notgotten used to driving again, and this imposes a great burden on theuser. If the transition point is set in a parking area or a rest area,the place in which the transition point can be set is limited, whichmakes a section where autonomous driving control can be performedunnecessarily short.

In order to solve the above conventional problems, it is an object ofexemplary embodiments of the broad inventive principles described hereinto provide an autonomous driving assist system, an autonomous drivingassist method, and a computer program, which reduce the burden that isimposed on the user when a transition from autonomous driving control tomanual driving using user's driving maneuvers is made and which preventa section where autonomous driving control is performed from becomingunnecessarily short.

Exemplary embodiments provide an autonomous vehicle driving assistsystem, method, and program that set a planned route of a vehicle, theplanned route including an autonomous driving section where autonomousdriving control of the vehicle is permitted, and set a transitionexclusion section of the planned route where a transition fromautonomous driving control to manual driving is determined to bedifficult. The system, method, and program set a transition section ofthe planned route where the transition from autonomous driving controlto manual driving is made, and which excludes the transition exclusionsection. Based on the transition section, the system, method, andprogram determine a section where autonomous driving control isperformed in the planned route.

According to the autonomous driving assist system, the autonomousdriving assist method, and the computer system having the aboveconfiguration, the transition section where a transition from autonomousdriving control to manual driving is made is set in the planned routeexcluding the section where a transition from autonomous driving controlto manual driving using user's driving maneuvers is determined to bedifficult to make. This can reduce the burden that is imposed on theuser when a transition from autonomous driving control to manual drivingis made. For example, the user is not required to perfoim complicatedmaneuvers or advanced maneuvers immediately after the transition, namelywhen he/she has not gotten used to driving again. This allows a smoothtransition from autonomous driving control to manual driving to be made,so that the vehicle can travel stably even after the transition tomanual driving. The place in which the transition section can be set isnot limited to a rest area or a parking area, and the transition sectioncan also be set on a mainline. This can prevent the section whereautonomous driving control is performed from becoming unnecessarilyshort.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of a navigationsystem according to a first embodiment.

FIG. 2 is a flowchart of an autonomous driving implementation sectionsetting program according to the first embodiment.

FIG. 3 is a diagram illustrating a method for setting a candidatetransition section.

FIG. 4 is a diagram showing an example of the content of autonomousdriving control that is set for a planned route of a vehicle.

FIG. 5 is a flowchart of an autonomous driving implementation sectionsetting program according to a second embodiment.

FIG. 6 is a diagram showing an example of a lane travel plan.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

An autonomous driving assist system will be described in detail based onfirst and second embodiments of a navigation system with reference tothe accompanying drawings.

First Embodiment

First, the general configuration of a navigation system 1 according to afirst embodiment will be described with reference to FIG. 1. FIG. 1 is ablock diagram of the navigation system 1 of the first embodiment.

As shown in FIG. 1, the navigation system 1 of the first embodiment isformed by: a current location detection unit 11 that detects the currentlocation of a vehicle equipped with the navigation system 1; a datarecording unit 12 having various data recorded thereon; a navigation ECU13 that performs various arithmetic operations based on receivedinformation; an operation unit 14 that accepts user's operation; aliquid crystal display 15 that displays to the user a map around thevehicle, information on a guide route (planned route of the vehicle) setby the navigation system 1, etc.; a speaker 16 that outputs voiceguidance about the route; a DVD drive 17 that reads a DVD, or a storagemedium; and a communication module 18 that communicates with aninformation center such as a probe center or a Vehicle Information andCommunication System (VICS (registered trademark)) center. Thenavigation system 1 is connected via an in-vehicle network such as a CANto an external camera 19 and various sensors which are mounted on thevehicle equipped with the navigation system 1. The navigation system 1is also connected to a vehicle control ECU 20 that performs variouscontrols on the vehicle equipped with the navigation system 1, such thatthe navigation system 1 and the vehicle control ECU 20 can communicatewith each other in two ways. The navigation system 1 is also connectedto various operation buttons 21 mounted on the vehicle, such as anautonomous driving switch and an autonomous driving start button.

Components of the navigation system 1 will be sequentially describedbelow.

The current location detection unit 11 is formed by a GPS 22, a vehiclespeed sensor 23, a steering sensor 24, a gyro sensor 25, etc. and candetect the current location and direction of the vehicle, the travelingspeed of the vehicle, the current time, etc. In particular, the vehiclespeed sensor 23 is a sensor that detects the distance traveled by thevehicle and the vehicle speed. The vehicle speed sensor 23 generatespulses according to rotation of drive wheels of the vehicle and outputsa pulse signal to the navigation ECU 13. The navigation ECU 13 countsthe number of generated pulses to calculate the rotational speed of thedrive wheels and the traveled distance. The navigation system 1 need notnecessarily include all of these four sensors. The navigation system 1may include only one or more of these sensors.

The data recording unit 12 includes a hard disk (not shown) as anexternal storage device and as a storage medium, and a recording head(not shown) that is a driver for reading a map information database DB31, a predetermined program, etc. recorded on the hard disk and writingpredetermined data on the hard disk. (As used herein, the terms “storagemedium” and “storage media” are not intended to encompass transitorysignals.) The data recording unit 12 may be formed by a memory card oran optical disk such as a CD or a DVD instead of the hard disk. The mapinformation DB 31 may be stored in an external server, and thenavigation system 1 may communicate with the external server to obtainthe map information DB 31.

The map information DB 31 is storage means having stored therein, e.g.,link data 33 relating to roads (links), node data 34 relating to nodepoints, search data 35 that is used for processing associated with aroute search or a route change, facility data relating to facilities,map display data for displaying a map, intersection data relating toeach intersection, search data for searching for locations, etc.

Data that is recorded as the link data 33 is: data on each link thatforms a road to which the link belongs, namely data indicating thewidth, slope, cant, and bank of the road, the road surface condition, amerging section, the road structure, whether or not there is anysidewall installed at the roadside, the number of lanes on the road, thelocation where the number of lanes decreases, the place where the roadwidth decreases, a railroad crossing, etc.; data on a corner, namelydata indicating the radius of curvature, an intersection, a T-junction,the entrance and exit of the corner, etc.; data on road attributes,namely data indicating a downhill road, an uphill road, etc.; and dataon road type, namely data indicating a local road such as a nationalhighway, a prefectural (state) road, or a narrow street, and a toll roadsuch as a national expressway, an urban expressway, an exclusiveautomobile road, a local toll road, or a toll bridge.

Data that is recorded as the node data 34 include data on: a branchpoint (including an intersection, a T-junction, etc.) of an actual road;the coordinates (positions) of node points set at predeterminedintervals on each road according to the radius of curvature etc.; nodeattributes indicating whether the node is a node corresponding to anintersection or not etc.; a connection link number list, or a list oflink numbers of links connecting to the node; an adjacent node numberlist, or a list of node numbers of nodes located adjacent to the nodewith a link therebetween; and the height (altitude) of each node point.

Various data that is used for a route search process of searching for aroute from a point of departure (e.g., the current location of thevehicle) to a set destination is recorded as the search data 35.Specifically, cost calculation data that is used to calculate searchcost such as cost obtained by converting level of appropriateness intonumbers as a route regarding an intersection (hereinafter referred to asthe “intersection cost”) and cost obtained by converting level ofappropriateness into numbers as a route regarding a link forming a road(hereinafter referred to as the “link cost”) is stored as the searchdata 35.

The navigation electronic control unit (ECU) 13 is an electronic controlunit that generally controls the navigation system 1. The navigation ECU13 includes: a CPU 41 as an arithmetic unit and a control unit; andinternal storage media such as a RAM 42 that is used as a working memorywhen the CPU 41 performs various arithmetic operations and that storesroute data etc. when a route search is conducted, a ROM 43 havingrecorded thereon an autonomous driving implementation section settingprogram (see FIG. 2) described below etc in addition to a controlprogram, and a flash memory 44 that stores a program read from the ROM43. The navigation ECU 13 forms various means as a processing algorithm.For example, route setting means sets a planned route of the vehicleincluding an autonomous driving section where autonomous driving controlof the vehicle is permitted. Exclusion section setting means sets, as atransition exclusion section, a section where a transition fromautonomous driving control to manual driving using user's drivingmaneuvers is determined to be difficult to make in the planned route.Transition section setting means sets a transition section where atransition from autonomous driving control to manual driving is made inthe planned route excluding the transition exclusion section. Autonomousdriving section deciding means decides a section where autonomousdriving control is performed in the planned route, according to thetransition section set by the transition section setting means. Manualdriving section obtaining means obtains a manual driving section wherethe vehicle needs to travel by manual driving in the planned route.Control content setting means sets the content of autonomous drivingcontrol to be performed on the vehicle in the section where autonomousdriving control is performed in the planned route.

The operation unit 14 is operated to enter a point of departure as astart point and a destination as an end point etc., and is formed by aplurality of operation switches (not shown) such as various keys andbuttons. The navigation ECU 13 performs control so as to execute variousoperations based on switch signals output in response to depression etc.of the switches. The operation unit 14 may be formed by a touch panelthat is provided on the front surface of the liquid crystal display 15.Alternatively, the operation unit 14 may be formed by a microphone and aspeech recognition device.

A map image including a road, traffic information, operation guidance,an operation menu, key guidance, guidance information according to aguide route (planned route), news, a weather forecast, time, an email, aTV program, etc. are displayed on the liquid crystal display 15. An HUDor an HMD may be used instead of the liquid crystal display 15.

The speaker 16 outputs voice guidance that tells the user the directionsalong a guide route based on a command from the navigation ECU 13, andguidance of traffic information.

The DVD drive 17 is a drive that can read data recorded on a recordingmedium such as a DVD or a CD. The DVD drive 17 plays music or images,updates the map information DB 31, etc. based on the read data.

The communication module 18 is a communication device that receivestraffic information, probe information, weather information, etc.transmitted from a traffic information center such as, e.g., a VICScenter or a probe center. For example, the communication module 18 is amobile phone or a DCM. Examples of the communication module 18 furtherinclude a vehicle-to-vehicle communication device for communicationbetween vehicles, and a road-to-vehicle communication device forcommunication between a vehicle and a roadside unit.

The external camera 19 is, e.g., a camera using a solid state imagingelement such as a CCD. The external camera 19 is attached to the vehicleat a position above a front bumper and is mounted such that its opticalaxis is tilted downward at a predetermined angle with respect to thehorizontal direction. The external camera 19 captures an image ahead ofthe vehicle in the traveling direction when the vehicle travels in anautonomous driving section. The vehicle control ECU 20 processes thecaptured image to detect pavement markings applied to the road on whichthe vehicle is traveling, other vehicles around, etc., and performsautonomous driving control of the vehicle based on the detection result.The external camera 19 may be placed on the rear or side part of thevehicle instead of on the front part of the vehicle. Instead of thecamera, a sensor such as a millimeter wave radar, vehicle-to-vehiclecommunication, or road-to-vehicle communication may be used as means fordetecting other vehicles.

Drive modes of the vehicle include a drive mode using autonomous drivingcontrol in which the vehicle autonomously travels along a preset routewithout user's driving maneuvers, in addition to a manual drive mode inwhich the vehicle travels based on user's driving maneuvers. Forexample, in autonomous driving control, the current location of thevehicle, the lane in which the vehicle is traveling, and the location ofother vehicles around are detected as needed, and vehicle control suchas control of steering, a driving source, and a brake is autonomouslyperformed by the vehicle control ECU 20 such that the vehicle travelsalong a preset route. Since autonomous driving control is already knownin the art, detailed description thereof will be omitted. Autonomousdriving control may be performed in all road sections. In the followingdescription, however, a freeway having gates (either manned or unmanned,and either toll or toll-free) at boundaries with other roads connectingto the freeway is set as an autonomous driving section where autonomousdriving control of the vehicle is performed, and the autonomous drivingcontrol is basically performed only when the vehicle is traveling in theautonomous driving section. Other sections may be set as an autonomousdriving section. For example, a national expressway, an urbanexpressway, an exclusive automobile road, a toll road, or a local roadmay be set as an autonomous driving section. Autonomous driving controlis not always performed when the vehicle travels in an autonomousdriving section, but is performed only when autonomous driving controlis selected by the user and only in a situation where it is appropriatefor the vehicle to travel by autonomous driving control. Namely, theautonomous driving section is a section where autonomous driving controlof the vehicle is permitted in addition to manual driving.

The vehicle control ECU 20 is an electronic control unit that controlsthe vehicle equipped with the navigation system 1. The vehicle controlECU 20 is connected to each driving part of the vehicle such assteering, a brake, and an accelerator. In the first embodiment, thevehicle control ECU 20 controls each driving part to perform autonomousdriving control of the vehicle particularly when the vehicle travels inan autonomous driving section. The navigation ECU 13 sends a commandsignal regarding autonomous driving control to the vehicle control ECU20 via a CAN when a planned route (guide route) of the vehicle has beendecided. The vehicle control ECU 20 performs autonomous driving controlafter the start of traveling according to the received command signal.The command signal contains information that specifies the planned route(guide route) and information that shows the set content of autonomousdriving control (e.g., travel straight, make a lane change to the right,merge, etc.) to be performed on the vehicle in an autonomous drivingsection included in the planned route. The navigation ECU 13 may sendthe content of autonomous driving control when a section whereautonomous driving control is performed has been decided as describedbelow, instead of when a planned route has been decided.

The autonomous driving implementation section setting program that isexecuted by the CPU 41 in the navigation system 1 of the firstembodiment having the above configuration will be described withreference to FIG. 2. FIG. 2 is a flowchart of the autonomous drivingimplementation section setting program according to the firstembodiment. The autonomous driving implementation section settingprogram is a program that is executed after a planned route (guideroute) of the vehicle is decided and that sets a section whereautonomous driving control is performed on the vehicle. The programshown in the flowchart of FIG. 2 is stored in the RAM 42 and the ROM 43of the navigation system 1 and is executed by the CPU 41.

In the autonomous driving implementation section setting program, theCPU 41 first obtains in step (hereinafter abbreviated as “S”) 1 aplanned route (guide route) currently set in the navigation system 1.For example, when the user starts driving, he/she sets a destination,whereby the CPU 41 obtains a plurality of route options by a routesearch process using known Dijkstra's algorithm, and the planned routeis decided from the plurality of route options by user's operation. Inthe following description, the planned route includes an autonomousdriving section, and the vehicle basically travels by autonomous drivingcontrol in the autonomous driving section unless the user intentionallycancels the autonomous driving control.

Next, in S2, the CPU 41 obtains from the map information DB 31 the roadstructure ahead of the vehicle in the traveling direction along theplanned route. The road structure obtained in S2 includes informationspecifying, in the case where there is a connection point of roads, howthe roads are connected at the connection point, information specifyinga merging section where the vehicle merges into traffic at theconnection point, whether there is any sidewall installed at theroadside, the curvature of a curve, the slope of the road surface, thecondition of the road surface (a step or a bad road), etc.

Then, in S3, the CPU 41 communicates with an external center via thecommunication module 18 to obtain weather information around thevehicle. The weather information includes information about rainfall,snowfall, and wind, etc. The weather may be detected by a rainfallsensor etc. mounted on the vehicle.

Thereafter, in S4, the CPU 41 obtains a manual driving section where thevehicle needs to travel by manual driving in the planned route. Themanual driving section includes a section that is not an autonomousdriving section (e.g., a freeway) and a section where it is difficultfor the vehicle to travel by autonomous driving control even within theautonomous driving section. The section where it is difficult for thevehicle to travel by autonomous driving control is specified based onthe road shape, pavement markings, traffic information, weatherinformation, past history of stopping of autonomous driving control,etc. For example, a section that meets any of the following conditions(1) to (5) is specified as the section where it is difficult for thevehicle to travel by autonomous driving control.

(1) A section where the vehicle needs to merge into traffic or make alane change within a short distance (e.g., 500 m or less).

(2) A section where a pavement marking (a centerline, a lane marking, aroadway edge marking, etc.) is missing or has faded to such a degreethat the pavement marking cannot be recognized by a camera.

(3) A section where there is a restricted lane due to an accident,construction work, a falling object, etc., but the restricted lanecannot be identified.

(4) A section where the weather is difficult to detect by a camera or asensor when the vehicle is traveling, or where it is difficult tocontrol the vehicle due to the weather (e.g., heavy rain, dense fog,fallen snow, or a frozen road surface).

(5) A section other than (1) to (4) where autonomous driving control wasstopped in the past.

In the case where the planned route of the vehicle has a plurality ofmanual driving sections, the CPU 41 may obtain all the manual drivingsections or may obtain only the manual driving section located ahead of,and closest to, the current location of the vehicle in the travelingdirection. In the following description, the CPU 41 obtains only themanual driving section located ahead of, and closest to, the currentlocation of the vehicle in the traveling direction.

Subsequently, in S5, the CPU 41 sets, as a transition exclusion section,a section where a transition from autonomous driving control to manualdriving using user's driving maneuvers is determined to be difficult tomake in the planned route. For example, the section where a transitionfrom autonomous driving control to manual driving is determined to bedifficult to make is a section where the burden of vehicle maneuvers tobe performed by the user after the transition to manual driving isgreater than a certain amount. The certain amount herein refers to theupper limit of the burden of maneuvers that can be appropriatelyperformed by a general user immediately after he/she starts driving. Forexample, the section where the burden of vehicle maneuvers to beperformed by the user after the transition to manual driving is greaterthan the certain amount is a section that meets any one of the followingconditions (A) to (D).

(A) A low visibility section where it is difficult to visually recognizesurrounding objects due to a sidewall installed at the roadside or badweather.

(B) A section with a bad road surface condition such as a step, a frozenroad surface, or an unpaved road.

(C) A section where a predetermined amount or more of break operation orsteering operation need be performed within a predetermined time due tomerging traffic, a road branching off, a curve, a slope, etc.

(D) A section where the wind is blowing hard (e.g., a wind speed of 15m/s or higher).

The CPU 41 may obtain all the transition exclusion sections included inthe planned route or may obtain only the transition exclusion sectionlocated ahead of the current location of the vehicle in the travelingdirection and before the manual driving section obtained in S4.

Subsequently, in S6, the CPU 41 sets a candidate transition section thatis a candidate for a transition section where a transition fromautonomous driving control to manual driving is made. In the plannedroute, a section that is located ahead of the current location of thevehicle in the traveling direction and before the start point of themanual driving section obtained in S4 and that is other than thetransition exclusion section is set as a candidate transition section.If there are a plurality of sections that can be set as a candidatetransition section, each of the sections is set as a candidatetransition section.

A method for setting a candidate transition section will be describedwith respect to, e.g., the case where the vehicle travels in a sectionhaving such a road structure that an interchange IC and a junction JCare successively located as shown in FIG. 3 along the planned route. Inthe example shown in FIG. 3, the vehicle enters a mainline 54 from aramp 53 at the IC and then enters another road 55 from the mainline 54at the JCT. The road 55 is not a road defined in the autonomous drivingsection. Namely, a section where the vehicle travels after it enters theroad 55 is obtained as a manual driving section in S4. A section fromthe start point of connection between the mainline 54 and the road 55 tothe point located a predetermined distance away from the start point ofconnection between the mainline 54 and the road 55 is a merging sectionwhere the vehicle merges into traffic. In this section, the user islikely to perform complicated vehicle maneuvers to merge into traffic.This section is therefore set as a transition exclusion section 61.Moreover, in a section from the point located a predetermined distancebefore the end point of connection between the mainline 54 and the road55 to the end point of connection between the mainline 54 and the road55, the user is likely to perform vehicle maneuvers to turn the vehicleor make a lane change as the road is branching off. Accordingly, thissection is also set as a transition exclusion section 62. As a result,sections 63, 64 are extracted as sections that are located ahead of thecurrent location of the vehicle in the traveling direction and beforethe start point of the manual driving section and that are other thanthe transition exclusion sections 61, 62. The sections 63, 64 are set ascandidate transition sections.

Thereafter, in S7, the CPU 41 determines, for each of the candidatetransition sections set in S6, if the length of the candidate transitionsection is equal to or greater than a predetermined distance,sequentially from the candidate transition section located closest tothe start point of the manual driving section. The predetermineddistance used in the determination in S7 is the lower limit of thedistance that allows a transition from autonomous driving control tomanual driving to be appropriately made. For example, the predetermineddistance is 500 m.

For example, in the example shown in FIG. 3, the CPU 41 first determinesif the length of the candidate transition section 63 located closest tothe start point of the manual driving section out of the candidatetransition sections 63, 64 is equal to or greater than the predetermineddistance. If the CPU 41 determines that the length of the candidatetransition section 63 is smaller than the predetermined distance, itsubsequently determines if the length of the candidate transitionsection 64 is equal to or greater than the predetermined length. The CPU41 repeatedly performs the determination process of S7 in a similarmanner until it finds a candidate transition section having a lengthequal to or greater than the predetermined distance.

If the CPU 41 determines that there is a candidate transition sectionfor which the length equal to or greater than the predetermined distancecan be secured (S7: YES), it sets the candidate transition section whichis located closest to the start point of the manual driving section andfor which the length equal to or greater than the predetermined distancecan be secured, as a transition section where a transition fromautonomous driving control to manual driving is made (S8).

Subsequently, in S9, the CPU 41 decides a section where autonomousdriving control is performed (hereinafter referred to as the “autonomousdriving implementation section”) in the planned route, according to thetransition section set in S8. Specifically, the autonomous drivingimplementation section is a section up to the start point of thetransition section set in S8 in the autonomous driving section. The CPU41 then sets the content of autonomous driving control (e.g., travelstraight, make a lane change to the right, merge, etc.) to be performedon the vehicle in the autonomous driving implementation section.

For example, FIG. 4 is a diagram showing an example of the content ofautonomous driving control that is set in the case where a section f ofthe planned route of the vehicle is set as a transition section andsections a to e of the planned route of the vehicle are autonomousdriving implementation sections. In the example shown in FIG. 4, thecontent of autonomous driving control are set for the sections a to e.The content of autonomous driving control is basically decided based onthe planned route and map information. For example, for a section wherethe vehicle needs to merge into a mainline at an IC etc., “merge” is setas the content of autonomous driving control. Moreover, “make a lanechange to the right (left)” is set for a section where the vehicle needsto make a lane change in order to move to another freeway at a JCT etc.The CPU 41 sends information specifying the planned route and the setcontent of autonomous driving control to the vehicle control ECU 20 viathe CAN. Accordingly, when the vehicle starts traveling, the vehiclecontrol ECU 20 performs autonomous driving control after the start oftraveling according to the information received from the navigationsystem 1.

If the CPU 41 deter nines that there is no candidate transition sectionfor which the length equal to or greater than the predetermined distancecan be secured (S7: NO), the routine proceeds to S10.

In S10, the CPU 41 informs the user that autonomous driving control ofthe vehicle is not going to be performed. The CPU 41 does not set anautonomous driving implementation section. That is, the vehicle does nottravel by autonomous driving control even if it subsequently enters theautonomous driving section.

As described in detail above, in the navigation system 1 according tothe first embodiment, the autonomous driving assist method using thenavigation system 1, and the computer program that is executed by thenavigation system 1, the navigation system 1 obtains a planned route ofthe vehicle including an autonomous driving section where autonomousdriving control of the vehicle is permitted (S1), sets, as a transitionexclusion section, a section where a transition from autonomous drivingcontrol to manual driving using user's driving maneuvers is determinedto be difficult to make in the planned route (S5), sets a transitionsection where a transition from autonomous driving control to manualdriving is made in the planned route excluding the transition exclusionsection (S8), and decides, according to the set transition section, asection where autonomous driving control is performed in the plannedroute (S9). This can reduce the burden that is imposed on the user whena transition from autonomous driving control to manual driving is made.For example, the user is not required to perform complicated maneuversor advanced maneuvers immediately after the transition, namely whenhe/she has not gotten used to driving again. This allows a smoothtransition from autonomous driving control to manual driving to be made,so that the vehicle can travel stably even after the transition tomanual driving. The place that can be set as a transition section is notlimited to a rest area or a parking area, and a mainline can also be setas a transition section. This can prevent the section where autonomousdriving control is performed from becoming unnecessarily short.

Second Embodiment

Next, a navigation system according to a second embodiment will bedescribed below with reference to FIGS. 5 and 6. In the followingdescription, the same reference characters as those in the configurationof the navigation system 1 of the first embodiment in FIGS. 1 to 4denote the same or corresponding portions as or to those in theconfiguration of the navigation system 1 of the first embodiment.

The general configuration of the navigation system of the secondembodiment is substantially the same as that of the navigation system 1of the first embodiment. Various control processes of the navigationsystem 1 of the second embodiment are also substantially the same asthose of the navigation system of the first embodiment. The navigationsystem of the second embodiment is different from that of the firstembodiment in that it also uses a lane travel plan, or a plan of how thevehicle travels in a lane when it travels along a planned route, to seta transition section where a transition from autonomous driving controlto manual driving is made.

An autonomous driving implementation section setting program that isexecuted by the CPU 41 in the navigation system of the second embodimentwill be described below with reference to FIG. 5, FIG. 5 is a flowchartof the autonomous driving implementation section setting programaccording to the second embodiment.

Since the processes of S21 to S26 are similar to those of S1 to S6 inthe autonomous driving implementation section setting program (FIG. 2)of the first embodiment, description thereof will be omitted.

Next, in S27, the CPU 41 obtains from the map information DB 31 the lanestructure ahead of the vehicle in the traveling direction along theplanned route. The lane structure obtained in S27 includes informationspecifying the number of lanes and an increase or decrease in the numberof lanes, etc.

Then, in S28, the CPU 41 creates a lane travel plan, or a plan of howthe vehicle travels in a lane when it travels along the planned route,based on the road structure obtained in S22 and the lane structureobtained in S27. In particular, the lane travel plan includes a plan ofhow the vehicle moves between lanes when it travels on a road having aplurality of lanes. FIG. 6 is a diagram showing an example of the lanetravel plan. The example of FIG. 6 shows a lane travel plan that iscarried out when the vehicle enters the mainline 54 from the ramp 53 atthe IC and then enters another road 55 from the mainline 54 at the JCT.In the lane travel plan, how the vehicle travels is basically decidedsuch that the vehicle does not make any lane change in a merging sectionwhere the vehicle merges into traffic. Since creation of the lane travelplan is already known in the art, detailed description thereof will beomitted. In the case where autonomous driving control of the vehicle isperformed, the autonomous driving control is performed such that thevehicle travels according to the created lane travel plan.

Thereafter, in S29, the CPU 41 specifies particularly a lane changesection where the vehicle makes a lane change in the lane travel plancreated in S28. For example, the lane travel plan shown in FIG. 6 hastwo lane changes, and the CPU 41 specifies sections 71, 72 as lanechange sections.

Subsequently, in S30 and S31, the CPU 41 determines, for each of thecandidate transition sections set in S26, if the length of the candidatetransition section is equal to or greater than a predetermined distanceand if the candidate transition section does not overlap the lane changesection in the lane travel plan, sequentially from the candidatetransition section located closest to the start point of the manualdriving section. The predetermined distance used in the determination inS30 is the lower limit of the distance that allows a transition fromautonomous driving control to manual driving to be appropriately made.For example, the predetermined distance is 500 m.

For example, in the example shown in FIG. 3, the CPU 41 first determinesif the length of the candidate transition section 63 located closest tothe start point of the manual driving section out of the candidatetransition sections 63, 64 is equal to or greater than the predetermineddistance and if the candidate transition section 63 does not overlap thelane change section. If the CPU 41 determines that the length of thecandidate transition section 63 is smaller than the predetermineddistance or that the candidate transition section 63 overlaps the lanechange section, it subsequently determines if the length of thecandidate transition section 64 is equal to or greater than thepredetermined length and if the candidate transition section 64 does notoverlap the lane change section. The CPU 41 repeatedly performs thedetermination processes of S30 and S31 in a similar manner until itfinds a candidate transition section that has a length equal to orgreater than the predetermined distance and that does not overlap thelane change section.

If the CPU 41 determines that there is a candidate transition sectionthat has a length equal to or greater than the predetermined distanceand that does not overlap the lane change section (530: YES, S31: NO),it sets the candidate transition section which is located closest to thestart point of the manual driving section, for which the length equal toor greater than the predetermined distance can be secured, and whichdoes not overlap the lane change section, as a transition section wherea transition from autonomous driving control to manual driving is made(S32).

Subsequently, in S33, the CPU 41 decides a section where autonomousdriving control is performed (hereinafter referred to as the “autonomousdriving implementation section”) in the planned route, according to thetransition section set in S32. Specifically, the autonomous drivingimplementation section is a section up to the start point of thetransition section set in S32 in the autonomous driving section. The CPU41 then sets the content of autonomous driving control (e.g., travelstraight, make a lane change to the right, merge, etc.) to be performedon the vehicle in the autonomous driving implementation section (seeFIG. 4).

If the CPU 41 determines that there is no candidate transition sectionfor which the length equal to or greater than the predetermined distancecan be secured and which does not overlap the lane change section (S30:NO, S31: YES), the routine proceeds to S34.

In S34, the CPU 41 informs the user that autonomous driving control ofthe vehicle is not going to be performed. The CPU 41 does not set anautonomous driving implementation section. That is, the vehicle does nottravel by autonomous driving control even if it subsequently enters theautonomous driving section.

As described in detail above, in the navigation system 1 according tothe second embodiment, the autonomous driving assist method using thenavigation system 1, and the computer program that is executed by thenavigation system 1, the navigation system 1 obtains a planned route ofthe vehicle including an autonomous driving section where autonomousdriving control of the vehicle is permitted (S21), sets, as a transitionexclusion section, a section where a transition from autonomous drivingcontrol to manual driving using user's driving maneuvers is determinedto be difficult to make in the planned route (S35), creates a lanetravel plan, or a plan of how the vehicle travels in a lane when ittravels along a planned route (S28), sets a transition section where atransition from autonomous driving control to manual driving is made inthe planned route excluding both the transition exclusion section and alane change section where the vehicle makes a lane change in the lanetravel plan (S32), and decides a section where autonomous drivingcontrol is performed in the planned route, according to the settransition section (S33). This can reduce the burden that is imposed onthe user when a transition from autonomous driving control to manualdriving is made. For example, the user is not required to performcomplicated maneuvers such as a lane change or advanced maneuversimmediately after the transition, namely when he/she has not gotten usedto driving again. This allows a smooth transition from autonomousdriving control to manual driving to be made, so that the vehicle cantravel stably even after the transition to manual driving. The placethat can be set as a transition section is not limited to a rest area ora parking area, and a mainline can also be set as a transition section.This can prevent the section where autonomous driving control isperformed from becoming unnecessarily short.

It should be understood that various improvements and modifications canbe made without departing from the spirit and scope of the broadinventive principles.

For example, in the first and second embodiments, the range in whichautonomous driving control is performed is decided from the sectionlocated ahead of the vehicle in the traveling direction along theplanned route when the vehicle is traveling. However, the range in whichautonomous driving control is performed may be decided from the entireplanned route at the time the planned route has been decided. That is,the CPU 41 may obtain all the manual driving sections included in theplanned route in S4 and S24 and may perform for each of the obtainedmanual driving sections the processes of S5 and the subsequent steps andthe processes of S25 and the subsequent steps.

In the second embodiment, the CPU 41 determines, for each candidatetransition section, if the length of the candidate transition section isequal to or greater than the predetermined distance and if the candidatetransition section does not overlap the lane change section (S30, S31).However, the CPU 41 may first determine for each candidate transitionsection only if the length of the candidate transition section is equalto or greater than the predetermined distance and tentatively decide asa transition section the candidate transition section located closest tothe start point of the manual driving section and having a length equalto or greater than the predetermined distance, and then determine if thetentatively decided transition section does not overlap the lane changesection.

In the first and second embodiments, the navigation system 1 sets thecontent of autonomous driving control (e.g., travel straight, make alane change to the right, merge, etc.) to be performed on the vehicle.However, the vehicle control ECU 20 may set the content of autonomousdriving control. The content of autonomous driving control need notnecessarily be set at the time a route search is conducted or at thetime an autonomous driving implementation section is decided. Thecontent of autonomous driving control need only be set by the time thevehicle reaches an autonomous driving section.

In the first and second embodiments, a control process in which thevehicle control ECU 20 controls all of an accelerator operation, a brakeoperation, and a steering wheel operation, which are the maneuversrelated to the behavior of the vehicle out of vehicle maneuvers, isdescribed as autonomous driving control that is performed such that thevehicle travels autonomously without user's driving maneuvers. However,autonomous driving control may be a control process in which the vehiclecontrol ECU 20 controls at least one of the accelerator operation, thebrake operation, and the steering wheel operation, which are themaneuvers related to the behavior of the vehicle out of the vehiclemaneuvers. Manual driving using user's driving maneuvers is described asa control process in which the user performs all of the acceleratoroperation, the brake operation, and the steering wheel operation, whichare the maneuvers related to the behavior of the vehicle out of thevehicle maneuvers.

In the first and second embodiments, the navigation system 1 executesthe autonomous driving implementation section setting program (FIG. 2).However, the vehicle control ECU 20 may execute the autonomous drivingimplementation section setting program. In this case, the vehiclecontrol ECU 20 obtains the current location of the vehicle, mapinformation, traffic information, etc. from the navigation system 1.

The inventive principles are applicable to devices having a route searchfunction, in addition to navigation systems. For example, exemplaryembodiments contemplate a mobile phone, a smartphone, a tablet computer,a personal computer, etc. (hereinafter referred to as the “mobileterminal etc.”). exemplary embodiments contemplate systems formed by aserver and the mobile terminal etc. In this case, each step of the aboveautonomous driving implementation section setting program (FIG. 2) maybe executed by either the server or the mobile terminal etc. In themobile terminal etc. embodiments, a vehicle capable of performingautonomous driving control and the mobile terminal etc. need beconnected (either wired or wireless) such that they can communicate witheach other.

Although the embodiments of the autonomous driving assist system aredescribed above, the autonomous driving assist system may have thefollowing configurations. In that case, the autonomous driving assistsystem has the following effects.

For example, a first configuration is as follows.

The autonomous driving assist system is characterized by including:route setting means for setting a planned route of a vehicle includingan autonomous driving section where autonomous driving control of thevehicle is permitted; exclusion section setting means for setting, as atransition exclusion section, a section where a transition fromautonomous driving control to manual driving using user's drivingmaneuvers is determined to be difficult to make in the planned route;transition section setting means for setting a transition section wherethe transition from autonomous driving control to manual driving is madein the planned route excluding the transition exclusion section; andautonomous driving section deciding means for deciding, according to thetransition section set by the transition section setting means, asection where autonomous driving control is performed in the plannedroute.

According to the autonomous driving assist system having the aboveconfiguration, the transition section where a transition from autonomousdriving control to manual driving using user's driving maneuvers is madeis set in the planned route excluding the section where a transitionfrom autonomous driving control to manual driving is determined to bedifficult to make. This can reduce the burden that is imposed on theuser when a transition from autonomous driving control to manual drivingis made. For example, the user is not required to perform complicatedmaneuvers or advanced maneuvers immediately after the transition, namelywhen he/she has not gotten used to driving again. This allows a smoothtransition from autonomous driving control to manual driving to be made,so that the vehicle can travel stably even after a transition to manualdriving. The place that can be set as the transition section is notlimited to a rest area or a parking area, and a mainline can also be setas the transition section. This can prevent the section where autonomousdriving control is performed from becoming unnecessarily short.

A second configuration is as follows.

The autonomous driving assist system is characterized in that theexclusion section setting means sets, as the transition exclusionsection, a section where a burden of a vehicle maneuver to be performedby the user after the transition to manual driving is greater than acertain amount.

According to the autonomous driving assist system having the aboveconfiguration, the transition section can be set such that the burden ofthe vehicle maneuver to be performed by the user immediately after atransition from autonomous driving control to manual driving is notlarge. Accordingly, the user can appropriately continue to drive thevehicle even immediately after such a transition, namely even whenhe/she has not gotten used to driving again.

A third configuration is as follows.

The autonomous driving assist system is characterized in that theexclusion section setting means sets, as the transition exclusionsection, a low visibility section, a section with a bad road surfacecondition, or a section where a predetermined amount or more of breakoperation or steering operation need be performed within a predeterminedtime.

According to the autonomous driving assist system having the aboveconfiguration, the user is not required to perform complicated maneuversor advanced maneuvers immediately after the transition, namely whenhe/she has not gotten used to driving again. This allows a smoothtransition from autonomous driving control to manual driving to be made,so that the vehicle can travel stably even after the transition tomanual driving.

A fourth configuration is as follows.

The autonomous driving assist system is characterized by furtherincluding: manual driving section obtaining means for obtaining a manualdriving section where the vehicle needs to travel by manual driving inthe planned route, wherein the transition section setting means sets, asthe transition section, a section which is located before a start pointof the manual driving section and closest to the start point of themanual driving section and for which a length equal to or greater than apredetermined distance can be secured, in the planned route excludingthe transition exclusion section.

According to the autonomous driving assist system having the aboveconfiguration, even if the planned route includes the manual drivingsection where the vehicle needs to travel by manual driving, thetransition section can be set so as to be located before the manualdriving section and to make a section where the vehicle travels byautonomous driving control as long as possible.

A fifth configuration is as follows.

The autonomous driving assist system is characterized by furtherincluding: plan creating means for creating a lane travel plan, or aplan of how the vehicle travels in a lane when it travels along theplanned route, wherein the transition section setting means sets thetransition section in view of the lane travel plan.

According to the autonomous driving assist system having the aboveconfiguration, a section where a complicated maneuver or an advancedmaneuver is required can be accurately specified in advance by using thelane travel plan. The transition section can therefore be set such thatthe user is not required to perform a complicated maneuver or anadvanced maneuver immediately after a transition, namely when he/she hasnot gotten used to driving again.

A sixth configuration is as follows.

The autonomous driving assist system is characterized by furtherincluding: lane change section specifying means for specifying a lanechange section, or a section where the vehicle makes a lane change inthe lane travel plan, wherein the transition section setting means setsthe transition section in the planned route excluding both thetransition exclusion section and the lane change section.

According to the autonomous driving assist system having the aboveconfiguration, particularly a section where the vehicle is required tomake a lane change can be accurately specified in advance by using thelane travel plan. The transition section can therefore be set such thatthe user is not required to perform a maneuver associated with a lanechange immediately after a transition, namely when he/she has not gottenused to driving again.

A seventh configuration is as follows.

The autonomous driving assist system is characterized by furtherincluding: control content setting means for setting a content ofautonomous driving control to be performed on the vehicle in the sectionwhere autonomous driving control is performed in the planned route.

According to the autonomous driving assist system having the aboveconfiguration, the content of autonomous driving control to be performedon the vehicle when it travels along the planned route can be set inview of the section where autonomous driving control is performed.

An eighth configuration is as follows.

The autonomous driving assist system is characterized by furtherincluding: autonomous driving section obtaining means for obtaining theautonomous driving section, wherein any manual driving section where thevehicle needs to travel by manual driving in the planned route of thevehicle is specified based on the autonomous driving section, and atleast the manual driving section located ahead of, and closest to, acurrent location of the vehicle in a traveling direction is obtained,and the transition section setting means sets the transition sectionbased on the obtained manual driving section and the transitionexclusion section.

According to the autonomous driving assist system having the aboveconfiguration, the transition section can be set based on the manualdriving section and the transition exclusion section.

A ninth configuration is as follows.

The autonomous driving assist system is characterized in that theexclusion section setting means sets a section where the vehicle mergesinto traffic as the transition exclusion section.

According to the autonomous driving assist system having the aboveconfiguration, the section where the vehicle merges into traffic can beset as the transition exclusion section.

1. An autonomous vehicle driving assist system, comprising: a processorprogrammed to: set a planned route of a vehicle, the planned routeincluding an autonomous driving section where autonomous driving controlof the vehicle is permitted; set a transition exclusion section of theplanned route where a transition from autonomous driving control tomanual driving is determined to be difficult; set a transition sectionof the planned route where the transition from autonomous drivingcontrol to manual driving is made and which excludes the transitionexclusion section; and based on the transition section, determine asection where autonomous driving control is performed in the plannedroute.
 2. The autonomous vehicle driving assist system according toclaim 1, wherein the processor is programmed to: set, as the transitionexclusion section, a section where a burden of a vehicle maneuver to beperformed by the user after the transition to manual driving is greaterthan a predetermined amount.
 3. The autonomous vehicle driving assistsystem according to claim 2, wherein the processor is programmed to:set, as the transition exclusion section, a low visibility section, asection with a bad road surface condition, or a section where apredetermined amount or more of break operation or steering operationneed to be performed within a predetermined time.
 4. The autonomousvehicle driving assist system according to claim 1, wherein theprocessor is programmed to: obtain a manual driving section where thevehicle needs to travel by manual driving in the planned route; and set,as the transition section, a section which is located before a startpoint of the manual driving section and closest to the start point ofthe manual driving section and for which a length equal to or greaterthan a predetermined distance can be secured, in the planned routeexcluding the transition exclusion section.
 5. The autonomous vehicledriving assist system according to claim 1, wherein the processor isprogrammed to: create a lane travel plan, or a plan of how the vehicletravels in a lane when it travels along the planned route; and set thetransition section in view of the lane travel plan.
 6. The autonomousvehicle driving assist system according to claim 5, wherein theprocessor is programmed to: specify a lane change section, or a sectionwhere the vehicle makes a lane change in the lane travel plan; and setthe transition section in the planned route excluding both thetransition exclusion section and the lane change section.
 7. Theautonomous vehicle driving assist system according to claim 1, whereinthe processor is programmed to: set a content of autonomous drivingcontrol to be performed on the vehicle in the section where autonomousdriving control is performed in the planned route.
 8. The autonomousvehicle driving assist system according to claim 7, wherein theprocessor is programmed to: obtain the autonomous driving section;specify any manual driving section where the vehicle needs to travel bymanual driving in the planned route of the vehicle based on the obtainedautonomous driving section; obtain at least the manual driving sectionlocated ahead of, and closest to, a current location of the vehicle in atraveling direction; and set the transition section based on theobtained manual driving section and the transition exclusion section. 9.The autonomous vehicle driving assist system according to claim 8,wherein the processor is programmed to: set a section where the vehiclemerges into traffic as the transition exclusion section.
 10. Anautonomous vehicle driving assist method, comprising: setting a plannedroute of a vehicle, the planned route including an autonomous drivingsection where autonomous driving control of the vehicle is permitted;setting a transition exclusion section of the planned route where atransition from autonomous driving control to manual driving isdetermined to be difficult; setting a transition section of the plannedroute where the transition from autonomous driving control to manualdriving is made, and which excludes the transition exclusion section;and based on the transition section, determining, a section whereautonomous driving control is performed in the planned route.
 11. Acomputer-readable storage medium storing an autonomous vehicle drivingassist program, as the program causing a computer to perform functionscomprising: setting a planned route of a vehicle, the planned routeincluding an autonomous driving section where autonomous driving controlof the vehicle is permitted; setting a transition exclusion section ofthe planned route where a transition from autonomous driving control tomanual driving is determined to be difficult; setting a transitionsection of the planned route where the transition from autonomousdriving control to manual driving is made, and which excludes thetransition exclusion section; and based on the transition section,determining a section where autonomous driving control is performed inthe planned route.